The scandal at the Internal Revenue Service is becoming more of a muddle. We're learning more this morning about which groups were targeted for extra scrutiny. Turns out both conservative groups and progressive groups were on the so-called Be on the Lookout List at the IRS. Meanwhile, the man currently leading the agency says an internal investigation has found no evidence of intentional wrong doing.

NPR's Tamara Keith has more.

TAMARA KEITH, BYLINE: The Be on the Lookout list or BOLO was at the center of the Inspector General's finding that Tea Party groups were improperly singled out for extra scrutiny. The reason they were flagged wasn't because of the contents of their applications, but rather because of their names. But it turns out Tea Party groups weren't the only ones on IRS BOLOs. A redacted list released by congressional Democrats shows systematic targeting of progressive groups and also open source software developers, groups related to the president's healthcare law, disputed territories in the Middle East and even medical marijuana.

The current head of the IRS, Danny Werfel, said on a conference call with reporters, the lists were wide ranging.

DANNY WERFEL: We discovered the existence of BOLO lists, which me and my team determined contained inappropriate criteria that was in use. And therefore, I took action to suspend the use of all BOLO lists.

KEITH: The memo went out late last week.

REPRESENTATIVE SANDER LEVIN: I think it very affects the narrative.

KEITH: Sander Levin is the ranking Democrat on the House Ways and Means Committee, one of the committees investigating the IRS targeting. For more than a month now, this has been a story about Tea Party groups being targeted. Some went so far as to call the scandal Nixonian, and accused President Obama of assembling an enemies list. Levin says he blames the Inspector General's failure to mention other groups given scrutiny.

LEVIN: It created a vacuum that I think allowed Republicans to politicize this issue, to try to connect it to the president, when there's no evidence whatsoever of any such a connection.

KEITH: In response to the BOLO list, showing progressives got scrutiny too, aides to the Republican chairmen of the two House committees investigating the IRS argue Tea Party groups had it worse. Jordan Sekulow, executive director of the American Center for Law and Justice, says knowing more groups were targeted by the IRS doesn't make it OK.

JORDAN SEKULOW: You know, wrong is wrong.

KEITH: Sekulow represents about 40 conservative groups who are suing the IRS for mistreatment.

SEKULOW: I'd encourage other groups to come forward. I mean we don't represent them, but the government trying to silence political speech is illegal. And it doesn't matter if they're trying to silence all of the speech or the conservative speech, which has been the focus so far.

KEITH: Progress Missouri is on a list of groups the IRS says got extra scrutiny and were ultimately granted tax-exempt status. It now appears likely Nicholson's group got that scrutiny because its name contained the word progress and its politics are progressive.

SOENDER: It certainly seems imprecise and clumsy the way they went about it. And based on our experience, they definitely looked at our activities, what we submitted. We provided a lot of documentation to the IRS showing what we are about and that we are, indeed, a non-partisan organization.

KEITH: He says he's neither offended nor validated to find out progressive groups like his were also on an IRS BOLO. What still isn't clear from the available evidence is how his experience and those of other progressive groups differed from those with Tea Party or patriot in their name. The acting head of the IRS Danny Werfel, made it clear, yesterday, the investigation - actually there are at least four of them - is very much ongoing.

WERFEL: We have no evidence that has emerged of any intentional wrongdoing by an IRS employee, and no evidence of any individuals outside of the IRS that were involved in these activities.

KEITH: Werfel appears before the House Ways and Means Committee later this week.